[en] The role of negative ions on Jeans instability in the presence of nonthermal positive ions has been investigated in this paper. Electrons and negative ions are considered Boltzmann-distributed, while the positive ions follow nonthermal velocity distribution. A negatively charged dust component is modeled by continuity and momentum equations. The linear dispersion relation shows that the presence of negative ions reduces the critical value of the nonthermal parameter a_cr, which consequently increases the unstable region and hence pronounces the Jeans instability. The growth rate of this Jeans instability decreases with the increasing negative ion temperature

[en] In this paper the effect of secondary electron emission on Jeans instability in a dusty plasma has been investigated. Due to secondary electron emission, dust grains may have two stable equilibrium states out of which one is negative and the other is positive. Here both cases have been considered separately. It has been shown that secondary electron emission enhances Jeans instability when equilibrium dust charge is negative. It has also been shown that growth rate of Jeans instability reduces with increasing secondary electron emission when equilibrium dust charge is positive

[en] The effect of magnetic field on the nonlinear growth rate of Rayleigh-Taylor instability induced two fluid interfacial structures has been investigated. The magnetic field is assumed to be parallel to the plane of the two fluid interface and acts in a direction perpendicular to the wave vector. If the magnetic field is restricted only to either side of the interface, the growth rate may be depressed (may almost disappear) or be enhanced depending on whether the magnetic pressure on the interface opposes the instability driving pressure difference g(ρ_h-ρ_l)y or acts in the same direction. If magnetic field is present on both sides of the two fluid interface, stabilization may also take place in the sense that the surface of separation undulates periodically when the force due to magnetic pressure on two sides is such as to act in opposite direction. This result differs from the classical linear theory result which predicts that the magnetic field parallel to the surface has no influence on the growth rate when the wave vector is perpendicular to its direction.

[en] Dust acoustic (DA) shock wave at high dust density, i.e., the dust electroacoustic (DEA) or dust Coulomb (DC) shock wave has been investigated incorporating the nonadiabatic dust charge variation. The nonlinear DEA (DC) shock wave is seen to be governed by the Korteweg-de Vries Burger equation, in which the Burger term is proportional to the nonadiabaticity generated dissipation. It is seen that the shock strength decreases but after reaching minimum, it increases as the dust space charge density |q_dn_d| increases and the shock strength of DA wave is greater than that of DEA (DC) wave. Moreover the DEA (DC) shock width increases appreciably with increase mass m_i of the ion component of the dusty plasma but for DA shock wave the effect is weak

[en] The combined effect of viscosity and vorticity on the growth rate of the bubble associated with single mode Rayleigh-Taylor instability is investigated. It is shown that the effect of viscosity on the motion of the lighter fluid associated with vorticity accumulated inside the bubble due to mass ablation may be such as to reduce the net viscous drag on the bubble exerted by the upper heavier fluid as the former rises through it.

[en] It is shown that in the presence of weak magnetic field, the dust lattice solitary wave in two-dimensional (2D) hexagonal dusty plasma crystal is governed by a gyration-modified 2D Korteweg-de Vries equation due to the action of Lorentz force on the dust particles. Numerical solutions reveal that only for weak magnetic field an apparently single hump solitary wave solution exist. But, for strong magnetic field dust lattice solitary wave becomes unstable showing repetitive solitary hump of increasing magnitude with time.

[en] The effect of surface tension on the Rayleigh-Taylor (RT) instability and Richtmyer - Meshkov (RM) instability induced development of nonlinear structures like spike and bubble at two fluid interface have been investigated. In case of RT instability, the surface tension reduces the velocity of the tip of both the bubble and the spike by the factor (1-k² /3 k_c²) where, k²_c = (ρ_h-ρ_l)g/T. For k² > 3 k_c², RT instability is stabilized. Any perturbation, whatever be its magnitude, results in stable large amplitude nonlinear oscillations. The RM instability is always stabilized by surface tension leading to nonlinear oscillation. Both the amplitude and the period of oscillation decreases monotonically as S = 12k²T / (ρ_h+ρ_l) increases where k is the wave number. The maximum height attained by the peak of the nonlinear interfacial structures (spike or bubble) increases approximately logarithmically with the initial interface velocity resulting from the shock.

[en] The role of streaming negative ions on the dust acoustic wave (DAW) propagation has been investigated based on orbit motion limited (OML) theory of dust grain charging. The complex plasma being assumed as composed of Boltzmanian electrons, inertial positive ions, streaming negative ions and the variable charge dust grains. Dust charge is assumed to be fluctuating. It is found that the dust acoustic wave becomes unstable when ratio of the thermal velocity with the streaming velocity of negative ions crosses some threshold value

[en] The effects of charging-delay and negative ions on nonlinear dust acoustic waves are investigated. It has been found that the charging-delay induced anomalous dissipation causes generation of dust acoustic collisionless shock waves in an electronegative dusty plasma. The small but finite amplitude wave is governed by a Korteweg-de Vries Burger equation in which the Burger term arises due to the charging-delay. Numerical investigations reveal that the charging-delay induced dissipation and shock strength decreases (increases) with the increase of negative ion concentration (temperature)

[en] The effects of both adiabatic and nonadiabatic charge variations on small but finite amplitude nonlinear dust acoustic wave (DAW) have been investigated in an electronegative dusty plasma in presence of a static magnetic field. It is found that in case of adiabatic charge variations, the nonlinear wave is governed by the Zakharov-Kuznetsov (ZK) equation which yields the usual solitary wave solution. On the other hand, in case of nonadiabatic charge variations, the dynamics is governed by the Zakharov-Kuznetsov-Burgers' (ZKB) equation which exhibits shock like structures. The results are discussed in the context of cometary plasma.